# Math Help - Geometry question on viewable degrees

1. ## Geometry question on viewable degrees

Could anyone help me understand the green question.

Thank you.

2. Originally Posted by McJ

Could anyone help me understand the green question.

Thank you.
Hello,

I've attached a sketch of the situation (see attachment)

The viewable angle of the earth looking from a satelite $S_a$ is twice as large as the angle $\alpha$.

The satelite, the center of the earth and the radius of the earth form a right triangle.

$\sin(\alpha)=\frac{R}{R+d}$

If you know d then you can calculate the viewable angle $= 2\cdot \alpha$ with R = 6365 km.

3. Thank you so much for your time.